Plasma processing apparatus

ABSTRACT

A disclosed plasma processing apparatus includes a substrate support. The substrate support has a first region configured to support a substrate and a second region configured to support an edge ring. The first electrode is provided in the first region. The second electrode is provided in the second region. The first bias power source is connected to the first electrode via the first circuit. The second bias power source is connected to the second electrode via the second circuit. The second circuit has impedance higher than impedance of the first circuit at a common bias frequency of a first electrical bias generated by the first bias power source and a second electrical bias generated by the second bias power source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority fromJapanese Patent Application No. 2020-046282 filed on Mar. 17, 2020, theentire contents of which are incorporated herein by reference.

FIELD

Exemplary embodiments of the present disclosure relate to a plasmaprocessing apparatus.

BACKGROUND

In the manufacture of electronic devices, a plasma processing apparatusis used. The plasma processing apparatus has a chamber and a substratesupport. The substrate support has a lower electrode and anelectrostatic chuck. The electrostatic chuck is provided on the lowerelectrode. The substrate support supports an edge ring. A substrate isplaced in a region surrounded by the edge ring on the substrate support.Radio frequency bias power is supplied to the lower electrode in orderto draw ions from plasma into the substrate. Japanese Unexamined PatentPublication No. 2019-36658 discloses such a plasma processing apparatus.

SUMMARY

In an exemplary embodiment, a plasma processing apparatus is provided.The plasma processing apparatus includes a chamber, a substrate support,a first bias power source, a second bias power source, a first circuit,and a second circuit. The substrate support has a first region, a secondregion, a first electrode, and a second electrode. The first region isconfigured to support a substrate. The second region is configured tosupport an edge ring. The first electrode is provided in the firstregion. The second electrode is provided in the second region andseparated from the first electrode. The first bias power source isconfigured to generate a first electrical bias and electricallyconnected to the first electrode. The second bias power source isconfigured to generate a second electrical bias and electricallyconnected to the second electrode. The first circuit is connectedbetween the first electrode and the first bias power source. The secondcircuit is connected between the second electrode and the second biaspower source. The second circuit has impedance higher than impedance ofthe first circuit at a common bias frequency of the first electricalbias and the second electrical bias.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, exemplaryembodiments, and features described above, further aspects, exemplaryembodiments, and features will become apparent by reference to thedrawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a plasma processing apparatus accordingto an exemplary embodiment.

FIG. 2 illustrates a configuration in a chamber of the plasma processingapparatus according to an exemplary embodiment.

FIG. 3 illustrates a first bias power source, a damping circuit, a firstcircuit, and a filter in a plasma processing apparatus according to anexemplary embodiment.

FIG. 4 illustrates a second bias power source, a damping circuit, asecond circuit, and a filter in a plasma processing apparatus accordingto an exemplary embodiment.

FIG. 5A is a diagram showing simulation results of voltage waveforms inthe plasma processing apparatus shown in FIG. 1, and FIG. 5B is adiagram showing simulation results of voltage waveforms in a plasmaprocessing apparatus of a comparative example.

FIG. 6 illustrates a first bias power source, a damping circuit, a firstcircuit, and a filter in a plasma processing apparatus according to anexemplary embodiment.

FIG. 7 illustrates a second bias power source, a damping circuit, asecond circuit, and a filter in a plasma processing apparatus accordingto an exemplary embodiment.

FIG. 8 schematically illustrates a plasma processing apparatus accordingto another exemplary embodiment.

FIG. 9 schematically illustrates a plasma processing apparatus accordingto still another exemplary embodiment.

DETAILED DESCRIPTION

Hereinafter, various exemplary embodiments will be described.

In an exemplary embodiment, a plasma processing apparatus is provided.The plasma processing apparatus includes a chamber, a substrate support,a first bias power source, a second bias power source, a first circuit,and a second circuit. The substrate support has a first region, a secondregion, a first electrode, and a second electrode. The first region isconfigured to support a substrate. The second region is configured tosupport an edge ring. The first electrode is provided in the firstregion. The second electrode is provided in the second region andseparated from the first electrode. The first bias power source isconfigured to generate a first electrical bias and electricallyconnected to the first electrode. The second bias power source isconfigured to generate a second electrical bias and electricallyconnected to the second electrode. The first circuit is connectedbetween the first electrode and the first bias power source. The secondcircuit is connected between the second electrode and the second biaspower source. The second circuit has impedance higher than impedance ofthe first circuit at a common bias frequency of the first electricalbias and the second electrical bias.

In the plasma processing apparatus of the above embodiment, the firstelectrode and the substrate form a first capacitor element. Further, thesecond electrode and the edge ring form a second capacitor element. Anarea of the edge ring is generally smaller than an area of thesubstrate. Therefore, the capacitance of the second capacitor element islower than the capacitance of the first capacitor element. Therefore,when an electric current that is supplied to the first capacitor elementand an electric current that is supplied to the second capacitor elementare the same as each other, the voltage waveform of the edge ringchanges at higher speed than the voltage waveform of the substrate. Inthe above embodiment, the first circuit is provided between the firstelectrode and the first bias power source, and the second circuit isprovided between the second electrode and the second bias power source.At the bias frequency, the impedance of the second circuit is higherthan the impedance of the first circuit. Therefore, the differencebetween the voltage waveform of the substrate and the voltage waveformof the edge ring is reduced.

In an exemplary embodiment, the impedance of the first circuit and theimpedance of the second circuit are set such that a ratio between anelectric current supplied to the substrate and an electric currentsupplied to the edge ring may be equal to a ratio between an area of thesubstrate and an area of the edge ring.

In an exemplary embodiment, the plasma processing may further include acontroller. The controller may be configured to control the second biaspower source to increase a setting level of the second electrical biasaccording to a decrease in a thickness of the edge ring and controls thesecond circuit to reduce the impedance of the second circuit accordingto the decrease in the thickness of the edge ring.

In an exemplary embodiment, each of the first electrical bias and thesecond electrical bias may be a pulse wave that is periodicallygenerated at a cycle that is defined by the bias frequency. The pulsewave includes a pulse of a negative voltage. The pulse of the negativevoltage may be a pulse of a negative direct-current voltage.

In an exemplary embodiment, each of the first electrical bias and thesecond electrical bias may be radio frequency power having the biasfrequency.

In an exemplary embodiment, the first circuit may have a first resistorand a first capacitor. The first resistor is connected between the firstelectrode and the first bias power source. The first capacitor isconnected between a node on an electrical path connecting the firstresistor with the first electrode and a ground. The second circuit mayhave a second resistor and a second capacitor. The second resistor isconnected between the second electrode and the second bias power source.The second capacitor is connected between a node on an electrical pathconnecting the second resistor with the second electrode and a ground.At least one of the second resistor or the second capacitor may bevariable.

In an exemplary embodiment, the first circuit may have a first inductorand a first capacitor. The first inductor is connected between the firstelectrode and the first bias power source. The first capacitor isconnected between a node on an electrical path connecting the firstinductor with the first electrode and a ground. The second circuit mayhave a second inductor and a second capacitor. The second inductor isconnected between the second electrode and the second bias power source.The second capacitor is connected between a node on an electrical pathconnecting the second inductor with the second electrode and a ground.At least one of the second inductor or the second capacitor may bevariable.

Hereinafter, various exemplary embodiments will be described in detailwith reference to the drawings. In the drawings, the same or equivalentportions are denoted by the same reference symbols.

FIG. 1 schematically illustrates a plasma processing apparatus accordingto an exemplary embodiment. A plasma processing apparatus 1 shown inFIG. 1 is provided with a chamber 10. FIG. 2 illustrates theconfiguration in the chamber of the plasma processing apparatusaccording to an exemplary embodiment. As shown in FIG. 2, the plasmaprocessing apparatus 1 may be a capacitively coupled plasma processingapparatus.

The chamber 10 provides an internal space 10 s therein. The central axisof the internal space 10 s is an axis AX which extends in the verticaldirection. In an embodiment, the chamber 10 includes a chamber body 12.The chamber body 12 has a substantially cylindrical shape. The internalspace 10 s is provided in the chamber body 12. The chamber body 12 isformed of, for example, aluminum. The chamber body 12 is electricallygrounded. A film having plasma resistance is formed on the inner wallsurface of the chamber body 12, that is, the wall surface defining theinternal space 10 s. This film may be a ceramic film such as a filmformed by anodization or a film formed of yttrium oxide.

A passage 12 p is formed in a side wall of the chamber body 12. Asubstrate W passes through the passage 12 p when it is transferredbetween the internal space 10 s and the outside of the chamber 10. Agate valve 12 g is provided along the side wall of the chamber body 12for opening and closing of the passage 12 p.

The plasma processing apparatus 1 is further provided with a substratesupport 16. The substrate support 16 is configured to support thesubstrate W placed thereon in the chamber 10. The substrate W has asubstantially disk shape. The substrate support 16 is supported by asupport 17. The support 17 extends upward from a bottom portion of thechamber body 12. The support 17 has a substantially cylindrical shape.The support 17 is formed of an insulating material such as quartz.

The substrate support 16 has a lower electrode 18 and an electrostaticchuck 20. The lower electrode 18 and the electrostatic chuck 20 areprovided in the chamber 10. The lower electrode 18 is formed of aconductive material such as aluminum and has a substantially disk shape.

A flow path 18 f is formed in the lower electrode 18. The flow path 18 fis a flow path for a heat exchange medium. As the heat exchange medium,for example, a liquid refrigerant is used. A supply device for the heatexchange medium (for example, a chiller unit) is connected to the flowpath 18 f. The supply device is provided outside the chamber 10. Theheat exchange medium is supplied from the supply device to the flow path18 f through a pipe 23 a. The heat exchange medium supplied to the flowpath 18 f is returned to the supply device through a pipe 23 b.

The electrostatic chuck 20 is provided on the lower electrode 18. Asshown in FIG. 1, the electrostatic chuck 20 has a dielectric portion 20d and an electrode 21 a. The electrostatic chuck 20 may further has anelectrode 22 a and an electrode 22 b. When the substrate W is processedin the internal space 10 s, the substrate W is placed on theelectrostatic chuck 20 and is held by the electrostatic chuck 20.Further, an edge ring ER is mounted on the substrate support 16. Theedge ring ER is a plate having a substantially ring shape. The edge ringER has electrical conductivity. The edge ring ER is formed of, forexample, silicon or silicon carbide. As shown in FIG. 2, the edge ringER is mounted on the substrate support 16 such that the central axisthereof coincides with the axis AX. The substrate W accommodated in thechamber 10 is disposed on the electrostatic chuck 20 and in a regionsurrounded by the edge ring ER.

The plasma processing apparatus 1 may be further provided with a gasline 25. The gas line 25 supplies a heat transfer gas, for example, a Hegas, from a gas supply mechanism to a gap between the upper surface ofthe electrostatic chuck 20 (a first region to be described later) andthe rear surface (lower surface) of the substrate W.

The plasma processing apparatus 1 may be further provided with an outerperipheral portion 28 and an outer peripheral portion 29. The outerperipheral portion 28 extends upward from the bottom portion of thechamber body 12. The outer peripheral portion 28 has a substantiallycylindrical shape and extends along the outer periphery of the support17. The outer peripheral portion 28 is formed of a conductive material.The outer peripheral portion 28 is electrically grounded. A film havingplasma resistance is formed on the surface of the outer peripheralportion 28. This film may be a ceramic film such as a film formed byanodization or a film formed of yttrium oxide.

The outer peripheral portion 29 is provided on the outer peripheralportion 28. The outer peripheral portion 29 is formed of a materialhaving insulation properties. The outer peripheral portion 29 is formedof ceramic such as quartz, for example. The outer peripheral portion 29has a substantially cylindrical shape. The outer peripheral portion 29extends along the outer peripheries of the lower electrode 18 and theelectrostatic chuck 20.

The plasma processing apparatus 1 is further provided with an upperelectrode 30. The upper electrode 30 is provided above the substratesupport 16. The upper electrode 30 closes an upper opening of thechamber body 12 together with a member 32. The member 32 has insulationproperties. The upper electrode 30 is supported on an upper portion ofthe chamber body 12 through the member 32.

The upper electrode 30 includes a ceiling plate 34 and a support 36. Thelower surface of the ceiling plate 34 defines the internal space 10 s. Aplurality of gas discharge holes 34 a are formed in the ceiling plate34. Each of the plurality of gas discharge holes 34 a penetrates theceiling plate 34 in a plate thickness direction (the verticaldirection). The ceiling plate 34 is formed of, for example, silicon.

Alternatively, the ceiling plate 34 may have a structure in which aplasma-resistant film is provided on the surface of a member made ofaluminum. This film may be a ceramic film such as a film formed byanodization or a film formed of yttrium oxide.

The support 36 detachably supports the ceiling plate 34. The support 36is formed of a conductive material such as aluminum, for example. A gasdiffusion chamber 36 a is provided in the interior of the support 36. Aplurality of gas holes 36 b extend downward from the gas diffusionchamber 36 a. The plurality of gas holes 36 b communicate with theplurality of gas discharge holes 34 a, respectively.

A gas introduction port 36 c is formed in the support 36. The gasintroduction port 36 c is connected to the gas diffusion chamber 36 a. Agas supply pipe 38 is connected to the gas introduction port 36 c.

A gas source group 40 is connected to the gas supply pipe 38 through avalve group 41, a flow rate controller group 42, and a valve group 43.The gas source group 40, the valve group 41, the flow rate controllergroup 42, and the valve group 43 configure a gas supply unit. The gassource group 40 includes a plurality of gas sources. Each of the valvegroup 41 and the valve group 43 includes a plurality of valves (forexample, on-off valves). The flow rate controller group 42 includes aplurality of flow rate controllers. Each of the plurality of flow ratecontrollers of the flow rate controller group 42 is a mass flowcontroller or a pressure control type flow rate controller. Each of theplurality of gas sources of the gas source group 40 is connected to thegas supply pipe 38 through a corresponding valve of the valve group 41,a corresponding flow rate controller of the flow rate controller group42, and a corresponding valve of the valve group 43. The plasmaprocessing apparatus 1 can supply gases from one or more gas sourcesselected from the plurality of gas sources of the gas source group 40 tothe internal space 10 s at individually adjusted flow rates.

A baffle plate 48 is provided between the outer peripheral portion 28and the side wall of the chamber body 12. The baffle plate 48 may beconfigured, for example, by coating a member made of aluminum withceramic such as yttrium oxide. A number of through-holes are formed inthe baffle plate 48. An exhaust pipe 52 is connected to the bottomportion of the chamber body 12 below the baffle plate 48. An exhaustdevice 50 is connected to the exhaust pipe 52. The exhaust device 50 hasa pressure controller such as an automatic pressure control valve, and avacuum pump such as a turbo molecular pump, and can reduce the pressurein the internal space 10s.

Hereinafter, the substrate support 16 will be described in detail. Asdescribed above, the substrate support 16 has the lower electrode 18 andthe electrostatic chuck 20. As shown in FIG. 1, the plasma processingapparatus 1 has a radio frequency power source 57. The radio frequencypower source 57 is connected to the lower electrode 18 through a matcher58. The radio frequency power source 57 is a power source that generatesradio frequency power for plasma generation. The radio frequency powergenerated by the radio frequency power source 57 has a frequency withinthe range of 27 to 100 MHz, for example, a frequency of 40 MHz or 60MHz. The matcher 58 has a matching circuit for matching the impedance onthe load side (the lower electrode 18 side) of the radio frequency powersource 57 with the output impedance of the radio frequency power source57. The radio frequency power source 57 may not be electricallyconnected to the lower electrode 18, and may be connected to the upperelectrode 30 through the matcher 58.

In the plasma processing apparatus 1, a radio frequency electric fieldis generated in the chamber 10 by the radio frequency power from theradio frequency power source 57. The gas in the chamber 10 is excited bythe generated radio frequency electric field. As a result, plasma isgenerated in the chamber 10. The substrate W is processed with chemicalspecies such as ions and/or radicals from the generated plasma.

The substrate support 16 has a first region 21 and a second region 22.The first region 21 is a central region of the substrate support 16. Thefirst region 21 includes the central region of the electrostatic chuck20 and the central region of the lower electrode 18. The second region22 extends in a circumferential direction on the outside in a radialdirection with respect to the first region 21. The second region 22includes a peripheral edge region of the electrostatic chuck 20 and aperipheral edge region of the lower electrode 18. In the plasmaprocessing apparatus 1, the first region 21 and the second region 22 areconfigured from a single electrostatic chuck and are integrated witheach other. In FIG. 1, the boundary between the first region 21 and thesecond region 22 is indicated by a broken line. In another embodiment,the first region 21 and the second region 22 may be configured fromindividual electrostatic chucks.

The first region 21 is configured to support the substrate W placedthereon (that is, on the upper surface thereof). The first region 21 isa region having a disk shape. The central axis of the first region 21substantially coincides with the axis AX. The first region 21 shares thedielectric portion 20 d with the second region 22. The dielectricportion 20 d is formed of a dielectric such as aluminum nitride oraluminum oxide. The dielectric portion 20 d has a substantially diskshape. In an embodiment, the thickness of the dielectric portion 20 d inthe second region 22 is smaller than the thickness of the dielectricportion 20 d in the first region 21. The position in the verticaldirection of the upper surface of the dielectric portion 20 d in thesecond region 22 may be lower than the position in the verticaldirection of the upper surface of the dielectric portion 20 d in thefirst region 21.

The first region 21 has the electrode 21 a (chuck electrode). Theelectrode 21 a is an electrode having a film shape and is provided inthe dielectric portion 20 d in the first region 21. A direct-currentpower source 55 is connected to the electrode 21 a through a switch 56.When a direct-current voltage from the direct-current power source 55 isapplied to the electrode 21 a, an electrostatic attraction force isgenerated between the first region 21 and the substrate W. Due to thegenerated electrostatic attraction force, the substrate W is attractedto the first region 21 and held by the first region 21.

The first region 21 further has a first electrode 21 c. The firstelectrode 21 c is an electrode having a film shape and is provided inthe dielectric portion 20 d in the first region 21. The electrode 21 amay extend closer to the upper surface of the first region 21 than thefirst electrode 21 c in the vertical direction.

The plasma processing apparatus 1 is further provided with a first biaspower source 61. The first bias power source 61 is electricallyconnected to the first electrode 21 c through a first circuit 63. Thefirst bias power source 61 generates a first electrical bias. The firstelectrical bias is applied to the first electrode 21 c. In anembodiment, the first electrical bias is a pulse wave that includes apulse of a negative direct-current voltage and is periodically generatedat a cycle that is defined by a bias frequency. The bias frequency maybe a frequency in the range of 200 kHz to 13.56 MHz. The voltage levelof the pulse wave may have a voltage value of 0 V or higher in a periodother than a period in which the pulse of the negative direct-currentvoltage continues in the cycle, and the pulse wave may be, for example,a pulse wave having a positive or negative voltage value. Alternatively,the voltage of the pulse wave may have an absolute value lower than theabsolute value of the voltage of the pulse in a period other than theperiod in which the pulse of the negative direct-current voltagecontinues in the cycle. The voltage level of the pulse may temporallychange within the cycle, and the pulse may be a pulse voltage such as atriangular wave or an impulse.

FIG. 3 illustrates a first bias power source, a damping circuit, a firstcircuit, and a filter in a plasma processing apparatus according to anexemplary embodiment. As shown in FIGS. 1 and 3, the plasma processingapparatus 1 may be further provided with a damping circuit 62 and afilter 64. The damping circuit 62 may be connected between the firstbias power source 61 and the first circuit 63. The filter 64 may beconnected between the first circuit 63 and the first electrode 21 c. Thefirst bias power source 61 may be connected to the first circuit 63without going through the damping circuit 62. In this case, the plasmaprocessing apparatus 1 may not be provided with the damping circuit 62.

As shown in FIG. 3, in an embodiment, the first bias power source 61includes a variable direct-current power source 61 p, a switch 61 a, anda switch 61 b. The variable direct-current power source 61 p is adirect-current power source that generates a negative direct-currentvoltage. The level of the direct-current voltage that is generated bythe variable direct-current power source 61 p is variable. The variabledirect-current power source 61 p is connected to an output 610 throughthe switch 61 a. The output 610 is connected to the ground through theswitch 61 b. The switch 61 a and the switch 61 b can be controlled by acontroller MC (described later). In a case where the switch 61 a is in aconduction state and the switch 61 b is in a non-conduction state, anegative direct-current voltage is output from the output 61 o. In acase where the switch 61 a is in the non-conduction state and the switch61 b is in the conduction state, the voltage level of the output 610becomes 0 V. A pulse wave, which is the first electrical bias, can beobtained by controlling the conduction state of each of the switch 61 aand the switch 61 b.

The damping circuit 62 is connected between the output 610 of the firstbias power source 61 and the first circuit 63. In an embodiment, thedamping circuit 62 has a resistor 62 r and a capacitor 62 c. One end ofthe resistor 62 r is connected to the output 610 of the first bias powersource 61. One end of the capacitor 62 c is connected to a node 62 n onan electrical path connecting the other end of the resistor 62 r withthe first circuit 63. The other end of the capacitor 62 c is grounded.

The impedance of the first circuit 63 may be variable. The first circuit63 has one or more variable circuit elements. Each of the one or morevariable circuit elements has a variable element parameter. In anembodiment, the first circuit 63 has a first variable resistor 63 r anda first variable capacitor 63 c as the one or more variable circuitelements. In the first circuit 63, the variable element parameters arethe resistance value of the first variable resistor 63 r and thecapacitance of the first variable capacitor 63 c. One end of the firstvariable resistor 63 r is connected to the output 610 of the first biaspower source 61 through the damping circuit 62. One end of the firstvariable capacitor 63 c is connected to a node 63 n on an electricalpath connecting the other end of the first variable resistor 63 r withthe first electrode 21 c. The other end of the first variable capacitor63 c is grounded. The impedance of the first circuit 63 is set by thecontroller MC. The impedance of the first circuit 63 is controlled bysetting the variable element parameter of each of one or more variablecircuit elements of the first circuit 63, for example, the resistancevalue of the first variable resistor 63 r and the capacitance of thefirst variable capacitor 63 c, by the controller MC. The impedance ofthe first circuit 63 may be constant rather than variable. That is, afixed resistor may be used instead of the first variable resistor 63 r,and a fixed capacitor may be used instead of the first variablecapacitor 63 c.

The filter 64 is connected between the node 63 n and the first electrode21 c. The filter 64 is an electric filter configured to block orattenuate the radio frequency power from the radio frequency powersource 57. The filter 64 includes, for example, an inductor connectedbetween the node 63 n and the first electrode 21 c.

As shown in FIG. 1, the second region 22 extends to surround the firstregion 21. The second region 22 is a substantially annular region. Thecentral axis of the second region 22 substantially coincides with theaxis AX. The second region 22 is configured to support the edge ring ERplaced thereon (that is, on the upper surface thereof). The secondregion 22 shares the dielectric portion 20 d with the first region 21.

In an embodiment, the second region 22 may hold the edge ring ER by anelectrostatic attraction force. In this embodiment, the second region 22may have one or more electrodes (chuck electrodes). In the embodimentshown in FIG. 1, the second region 22 has a pair of electrodes, that is,the electrode 22 a and the electrode 22 b. The electrode 22 a and theelectrode 22 b are provided in the dielectric portion 20 d in the secondregion 22. The electrode 22 a and the electrode 22 b configure a bipolarelectrode. Each of the electrode 22 a and the electrode 22 b is anelectrode having a film shape. The electrode 22 a and the electrode 22 bmay extend at substantially the same height position in the verticaldirection.

A direct-current power source 71 is connected to the electrode 22 athrough a switch 72 and a filter 73. The filter 73 is an electric filterconfigured to block or attenuate the radio frequency power and the firstand second electrical biases. A direct-current power source 74 isconnected to the electrode 22 b through a switch 75 and a filter 76. Thefilter 76 is an electric filter configured to block or reduce the radiofrequency power and the first and second electrical biases.

The direct-current power source 71 and the direct-current power source74 apply direct-current voltages to the electrodes 22 a and 22 b,respectively, in order to generate an electrostatic attraction forcethat attracts the edge ring ER to the second region 22. The settingpotential of each of the electrodes 22 a and 22 b may be any of positivepotential, negative potential, and 0 V. For example, the potential ofthe electrode 22 a may be set to positive potential, and the potentialof the electrode 22 b may be set to negative potential. Further, thepotential difference between the electrode 22 a and the electrode 22 bmay be formed by using a single direct-current power source instead ofthe two direct-current power sources.

When a direct-current voltage is applied to the electrode 22 a and theelectrode 22 b, an electrostatic attraction force is generated betweenthe second region 22 and the edge ring ER. The edge ring ER is attractedto the second region 22 by the generated electrostatic attraction forceand held by the second region 22.

The second region 22 further has a second electrode 22 c. The secondelectrode 22 c is an electrode having a film shape. The second electrode22 c is provided in the dielectric portion 20 d in the second region 22.The second electrode 22 c is separated from the first electrode 21 c.The electrode 22 a and the electrode 22 b may extend closer to the uppersurface of the second region 22 than the second electrode 22 c in thevertical direction. The second electrode 22 c may be disposed outsidethe second region 22. For example, the second electrode 22 c may beprovided below the edge ring ER and in the outer peripheral portion 29.

The plasma processing apparatus 1 is further provided with a second biaspower source 81. The second bias power source 81 is electricallyconnected to the second electrode 22 c through a second circuit 83. Thesecond bias power source 81 generates a second electrical bias. Thesecond electrical bias is applied to the second electrode 22 c. In anembodiment, the second electrical bias is a pulse wave that includes apulse of a negative direct-current voltage and is periodically generatedat a cycle that is defined by the bias frequency. The bias frequency ofthe second electrical bias is the same as the bias frequency of thefirst electrical bias. The voltage level of the pulse wave may have avoltage value of 0 V or higher in a period other than a period in whichthe pulse of the negative direct-current voltage continues in the cycle,and the pulse wave may be, for example, a pulse wave having a positiveor negative voltage value. Alternatively, the voltage of the pulse wavemay have an absolute value lower than the absolute value of the voltageof the pulse in a period other than the period in which the pulse of thenegative direct-current voltage continues in the cycle. The voltagelevel of the pulse may temporally change within the cycle, and the pulsemay be a pulse voltage such as a triangular wave or an impulse.

FIG. 4 illustrates a second bias power source, a damping circuit, asecond circuit, and a filter in a plasma processing apparatus accordingto an exemplary embodiment. As shown in FIGS. 1 and 4, the plasmaprocessing apparatus 1 may be further provided with a damping circuit 82and a filter 84. The damping circuit 82 may be connected between thesecond bias power source 81 and the second circuit 83. The filter 84 maybe connected between the second circuit 83 and the second electrode 22c. The second bias power source 81 may be connected to the secondcircuit 83 without going through the damping circuit 82. In this case,the plasma processing apparatus 1 may not be provided with the dampingcircuit 82.

As shown in FIG. 4, in an embodiment, the second bias power source 81includes a variable direct-current power source 81 p, a switch 81 a, anda switch 81 b. The variable direct-current power source 81 p is adirect-current power source that generates a negative direct-currentvoltage. The level of the direct-current voltage that is generated bythe variable direct-current power source 81 p is variable. The variabledirect-current power source 81 p is connected to an output 810 throughthe switch 81 a. The output 810 is connected to the ground through theswitch 81 b. The switch 81 a and the switch 81 b can be controlled bythe controller MC (described later). In a case where the switch 81 a isin a conduction state and the switch 81 b is in a non-conduction state,a negative direct-current voltage is output from the output 81 o. In acase where the switch 81 a is in the non-conduction state and the switch81 b is in the conduction state, the voltage level of the output 810becomes 0 V. A pulse wave, which is the second electrical bias, can beobtained by controlling the conduction state of each of the switch 81 aand the switch 81 b.

The damping circuit 82 is connected between the output 810 of the secondbias power source 81 and the second circuit 83. In an embodiment, thedamping circuit 82 has a resistor 82 r and a capacitor 82 c. One end ofthe resistor 82 r is connected to the output 810 of the second biaspower source 81. One end of the capacitor 82 c is connected to a node 82n on an electrical path connecting the other end of the resistor 82 rwith the second circuit 83. The other end of the capacitor 82 c isgrounded.

The impedance of the second circuit 83 may be variable. The secondcircuit 83 has one or more variable circuit elements. Each of the one ormore variable circuit elements has a variable element parameter. In anembodiment, the second circuit 83 has a second variable resistor 83 rand a second variable capacitor 83 c as the one or more variable circuitelements. In the second circuit 83, the variable element parameters arethe resistance value of the second variable resistor 83 r and thecapacitance of the second variable capacitor 83 c.

One end of the second variable resistor 83 r is connected to the output810 of the second bias power source 81 through the damping circuit 82.One end of the second variable capacitor 83 c is connected to a node 83n on an electrical path connecting the other end of the second variableresistor 83 r with the second electrode 22 c. The other end of thesecond variable capacitor 83 c is grounded. The second circuit 83 hasimpedance higher than the impedance of the first circuit 63 at a commonbias frequency of the first electrical bias and the second electricalbias. In an embodiment, the impedance of the first circuit 63 and theimpedance of the second circuit 83 are set such that the ratio betweenan electric current that is supplied to the substrate W and an electriccurrent that is supplied to the edge ring ER is equal to the ratiobetween an area of the substrate W and an area of the edge ring ER. Theimpedance of the second circuit 83 is set by the controller MC. Theimpedance of the second circuit 83 is controlled by setting the variableelement parameter of each of one or more variable circuit elements ofthe second circuit 83, for example, the resistance value of the secondvariable resistor 83 r and the capacitance of the second variablecapacitor 83 c, by the controller MC. The impedance of the secondcircuit 83 may be constant rather than variable. That is, a fixedresistor may be used instead of the second variable resistor 83 r, and afixed capacitor may be used instead of the second variable capacitor 83c.

The filter 84 is connected between the node 83 n and the secondelectrode 22 c. The filter 84 is an electric filter configured to blockor attenuate the radio frequency power from the radio frequency powersource 57. The filter 84 includes, for example, an inductor connectedbetween the node 83 n and the second electrode 22 c.

The second region 22 may further have a gas line 22 g. The gas line 22 gis a gas line provided for supplying a heat transfer gas, for example, aHe gas, to the gap between the second region 22 and the edge ring ER.The gas line 22 g is connected to a gas supply mechanism 86 which is aheat transfer gas source.

In an embodiment, as shown in FIG. 2, the plasma processing apparatus 1is further provided with the controller MC. The controller MC is acomputer which includes a processor, a storage device, an input device,a display device, and the like, and controls each part of the plasmaprocessing apparatus 1. Specifically, the controller MC executes acontrol program stored in the storage device, and controls each part ofthe plasma processing apparatus 1, based on recipe data stored in thestorage device. The process designated by the recipe data is performedin the plasma processing apparatus 1 under the control by the controllerMC.

Here, the edge ring ER wears by being exposed to plasma, so that thethickness thereof decreases. In a case where the thickness of the edgering ER becomes smaller than the initial thickness thereof, the upperend of a sheath (plasma sheath) is inclined in the vicinity of an edgeof the substrate W. Therefore, in a case where the thickness of the edgering ER becomes smaller than the initial thickness thereof, an incidentdirection of ions with respect to the edge of the substrate W isinclined with respect to the vertical direction. In an embodiment, thecontroller MC may control the second bias power source 81 to increasethe setting level of the second electrical bias according to a decreasein the thickness of the edge ring ER. In a case where the secondelectrical bias is the pulse wave described above, the setting level ofthe second electrical bias is the absolute value of the voltage of thepulse in the pulse wave. When the setting level of the second electricalbias is increased, the thickness of the sheath increases above the edgering ER, so that the inclination of the incident direction of the ionswith respect to the edge of the substrate W can be corrected.

The controller MC may specify the setting level of the second electricalbias corresponding to the thickness of the edge ring ER by using afunction or a table stored in the storage device thereof. The thicknessof the edge ring ER may be measured optically or electrically, or may beestimated from a time in which the edge ring ER is exposed to plasma.

Further, the controller MC may control the variable element parameter ofeach of the one or more variable circuit elements of the second circuit83 to reduce the impedance of the second circuit 83 according to thedecrease in the thickness of the edge ring ER. The impedance of thesecond circuit 83 is reduced according to an increase in the settinglevel of the second electrical bias, whereby an increase in a timelength that is required to reach a peak level from a base level in thevoltage waveform of the edge ring ER is suppressed.

In an embodiment, the controller MC may specify the variable elementparameter of each of the one or more variable circuit elements of thesecond circuit 83 corresponding to the setting level of the secondelectrical bias by using a function or a table stored in the storagedevice thereof. The variable element parameter of each of the one ormore variable circuit elements of the second circuit 83 corresponding tothe thickness of the edge ring ER may be directly associated with thethickness of the edge ring ER.

In the plasma processing apparatus 1, the first electrode 21 c and thesubstrate W form a first capacitor element. Further, the secondelectrode 22 c and the edge ring ER form a second capacitor element. Theregion of the edge ring ER is smaller than the region of the substrateW. Therefore, the capacitance of the second capacitor element is lowerthan the capacitance of the first capacitor element. Therefore, when anelectric current that is supplied to the first capacitor element and anelectric current that is supplied to the second capacitor element arethe same as each other, the voltage waveform of the edge ring ER changesat a higher speed than the voltage waveform of the substrate W. In theplasma processing apparatus 1, the first circuit 63 is provided betweenthe first electrode 21 c and the first bias power source 61, and thesecond circuit 83 is provided between the second electrode 22 c and thesecond bias power source 81. At the bias frequency, the impedance of thesecond circuit 83 is set to impedance higher than the impedance of thefirst circuit 63. Therefore, according to the plasma processingapparatus 1, the difference between the voltage waveform of thesubstrate W and the voltage waveform of the edge ring ER is reduced.

Hereinafter, FIGS. 5A and 5B will be referred to. FIG. 5A is a diagramshowing simulation results of voltage waveforms in the plasma processingapparatus shown in FIG. 1. FIG. 5B is a diagram showing simulationresults of voltage waveforms in a plasma processing apparatus of acomparative example. The plasma processing apparatus of the comparativeexample is a plasma processing apparatus in which the first circuit 63and the second circuit 83 are removed from the plasma processingapparatus 1. In each of FIGS. 5A and 5B, the horizontal axis representstime and the vertical axis represents voltage. In each of FIGS. 5A and5B, the waveform of the output voltage (the second electrical bias) ofthe second bias power source 81, the voltage waveform of the edge ringER, and the voltage waveform of the substrate W are respectivelyindicated by a dashed-dotted line, a solid line, and a broken line. Asshown in FIG. 5B, in the plasma processing apparatus of the comparativeexample which does not have the first circuit 63 and the second circuit83, a difference occurs between the voltage waveform of the substrate Wand the voltage waveform of the edge ring ER. On the other hand, asshown in FIG. 5A, in the plasma processing apparatus 1, the differencebetween the voltage waveform of the substrate W and the voltage waveformof the edge ring ER is reduced.

Hereinafter, FIGS. 6 and 7 will be referred to. FIG. 6 illustrates afirst bias power source, a damping circuit, a first circuit, and afilter in a plasma processing apparatus according to an exemplaryembodiment. FIG. 7 illustrates a second bias power source, a dampingcircuit, a second circuit, and a filter in a plasma processing apparatusaccording to an exemplary embodiment. As shown in FIG. 6, the firstcircuit 63 may have a first variable inductor 63i instead of the firstvariable resistor 63 r. Further, as shown in FIG. 7, the second circuit83 may have a second variable inductor 83 i instead of the secondvariable resistor 83 r. Although the example in which the first circuitand the second circuit include the variable elements is shown, the firstcircuit and/or the second circuit may not include the variable element.

Hereinafter, FIG. 8 will be referred to. FIG. 8 schematicallyillustrates a plasma processing apparatus according to another exemplaryembodiment. A plasma processing apparatus 1B shown in FIG. 8 includes aradio frequency bias power source as the first bias power source 61. Theplasma processing apparatus 1B includes a radio frequency bias powersource as the second bias power source 81. In the plasma processingapparatus 1B, the first bias power source 61 is configured to generateradio frequency bias power having a bias frequency as the firstelectrical bias. The bias frequency is a frequency within the range of200 kHz to 13.56 MHz, and is, for example, 400 kHz. In the plasmaprocessing apparatus 1B, the first bias power source 61 is connected tothe first electrode 21 c through a matcher 65 and the first circuit 63.The matcher 65 has a matching circuit for matching the impedance on theload side of the first bias power source 61 with the output impedance ofthe first bias power source 61.

Further, in the plasma processing apparatus 1B, the second bias powersource 81 is configured to generate radio frequency bias power having abias frequency as the second electrical bias. The bias frequency of theradio frequency bias power that is generated by the second bias powersource 81 is the same as the bias frequency of the radio frequency biaspower that is generated by the first bias power source 61. Further, inthe plasma processing apparatus 1B, the second bias power source 81 isconnected to the second electrode 22 c through a matcher 85 and thesecond circuit 83. The matcher 85 has a matching circuit for matchingthe impedance on the load side of the second bias power source 81 withthe output impedance of the second bias power source 81. In the plasmaprocessing apparatus 1B, the setting level of the second electrical biasthat is controlled by the controller MC is a power level of the radiofrequency bias power. Other configurations of the plasma processingapparatus 1B may be the same as the corresponding configurations of theplasma processing apparatus 1.

Hereinafter, FIG. 9 will be referred to. FIG. 9 schematicallyillustrates a plasma processing apparatus according to still anotherexemplary embodiment. In a plasma processing apparatus 1C shown in FIG.9, the electrode 22 a and the electrode 22 b are used as the secondelectrode 22 c. The electrical path extending from the output of thesecond bias power source 81 is branched into two branch paths in asubsequent stage of the second circuit 83 (or the filter 84), and thetwo branch paths are respectively connected to the electrode 22 a andthe electrode 22 b through blocking capacitors 87 a and 87 b. Otherconfigurations of the plasma processing apparatus 1C may be the same asthe corresponding configurations of the plasma processing apparatus 1.Also in the plasma processing apparatus 1B, similar to the plasmaprocessing apparatus 1C, the electrodes 22 a and 22 b may be used as thesecond electrode to which the second electrical bias is applied, and thesecond electrode 22 c separate from the electrodes 22 a and 22 b may beomitted.

While various exemplary embodiments have been described above, variousadditions, omissions, substitutions and changes may be made withoutbeing limited to the exemplary embodiments described above. Elements ofthe different embodiments may be combined to form another embodiment.

For example, in another embodiment, the plasma processing apparatus maybe a capacitively coupled plasma processing apparatus different from theplasma processing apparatus 1. In another embodiment, the plasmaprocessing apparatus may be another type of plasma processing apparatus.The other type of plasma processing apparatus may be an inductivelycoupled plasma processing apparatus, an electron cyclotron resonance(ECR) plasma processing apparatus, or a plasma processing apparatus thatgenerates plasma by using surface waves such as microwaves.

Further, the first electrode 21 c and the second electrode 22 c may notbe provided in the dielectric portion 20 d of the electrostatic chuck20. Each of the first electrode 21 c and the second electrode 22 c maybe provided in another dielectric portion provided between theelectrostatic chuck 20 and the lower electrode 18.

Further, each of the one or more variable circuit elements in each ofthe first circuit 63 and the second circuit 83 is not a single variablecircuit element, but may be configured with an array of a plurality offixed circuit elements and a plurality of switching elementsrespectively connected to the plurality of fixed circuit elements. Inthis case, the number of fixed circuit elements that are connected inparallel is adjusted by controlling the plurality of switching elements.

From the foregoing description, it will be appreciated that variousembodiments of the present disclosure have been described herein forpurposes of illustration, and that various modifications may be madewithout departing from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A plasma processing apparatus comprising: achamber; a substrate support provided in the chamber and having a firstregion configured to support a substrate, a second region configured tosupport an edge ring, a first electrode provided in the first region,and a second electrode provided in the second region and separated fromthe first electrode; a first bias power source configured to generate afirst electrical bias and electrically connected to the first electrode;a second bias power source configured to generate a second electricalbias and electrically connected to the second electrode; a first circuitconnected between the first electrode and the first bias power source;and a second circuit connected between the second electrode and thesecond bias power source and having impedance higher than impedance ofthe first circuit at a common bias frequency of the first electricalbias and the second electrical bias.
 2. The plasma processing apparatusaccording to claim 1, wherein the impedance of the first circuit and theimpedance of the second circuit are set such that a ratio between anelectric current supplied to the substrate and an electric currentsupplied to the edge ring is equal to a ratio between an area of thesubstrate and an area of the edge ring.
 3. The plasma processingapparatus according to claim 1, further comprising: a controllerconfigured to control the second bias power source and the secondcircuit, wherein the controller is configured to control the second biaspower source to increase a setting level of the second electrical biasaccording to a decrease in a thickness of the edge ring and controls thesecond circuit to reduce the impedance of the second circuit accordingto the decrease in the thickness of the edge ring.
 4. The plasmaprocessing apparatus according to claim 2, further comprising: acontroller configured to control the second bias power source and thesecond circuit, wherein the controller is configured to control thesecond bias power source to increase a setting level of the secondelectrical bias according to a decrease in a thickness of the edge ringand controls the second circuit to reduce the impedance of the secondcircuit according to the decrease in the thickness of the edge ring. 5.The plasma processing apparatus according to claim 1, wherein each ofthe first electrical bias and the second electrical bias is a pulse wavethat includes a pulse of a negative voltage and is periodicallygenerated at a cycle that is defined by the bias frequency.
 6. Theplasma processing apparatus according to claim 5, wherein the pulse ofthe negative voltage is a pulse of a negative direct-current voltage. 7.The plasma processing apparatus according to claim 1, wherein each ofthe first electrical bias and the second electrical bias is radiofrequency power having the bias frequency.
 8. The plasma processingapparatus according to claim 1, wherein the first circuit has a firstresistor connected between the first electrode and the first bias powersource, and a first capacitor connected between a node on an electricalpath connecting the first resistor with the first electrode and aground, and the second circuit has a second resistor connected betweenthe second electrode and the second bias power source, and a secondcapacitor connected between a node on an electrical path connecting thesecond resistor with the second electrode and a ground.
 9. The plasmaprocessing apparatus according to claim 8, wherein at least one of thesecond resistor or the second capacitor is variable.
 10. The plasmaprocessing apparatus according to claim 5, wherein the first circuit hasa first resistor connected between the first electrode and the firstbias power source, and a first capacitor connected between a node on anelectrical path connecting the first resistor with the first electrodeand a ground, and the second circuit has a second resistor connectedbetween the second electrode and the second bias power source, and asecond capacitor connected between a node on an electrical pathconnecting the second resistor with the second electrode and a ground.11. The plasma processing apparatus according to claim 10, wherein atleast one of the second resistor or the second capacitor is variable.12. The plasma processing apparatus according to claim 1, wherein thefirst circuit has a first inductor connected between the first electrodeand the first bias power source, and a first capacitor connected betweena node on an electrical path connecting the first inductor with thefirst electrode and a ground, and the second circuit has a secondinductor connected between the second electrode and the second biaspower source, and a second capacitor connected between a node on anelectrical path connecting the second inductor with the second electrodeand a ground.
 13. The plasma processing apparatus according to claim 12,wherein at least one of the second inductor or the second capacitor isvariable.
 14. The plasma processing apparatus according to claim 5,wherein the first circuit has a first inductor connected between thefirst electrode and the first bias power source, and a first capacitorconnected between a node on an electrical path connecting the firstinductor with the first electrode and a ground, and the second circuithas a second inductor connected between the second electrode and thesecond bias power source, and a second capacitor connected between anode on an electrical path connecting the second inductor with thesecond electrode and a ground.
 15. The plasma processing apparatusaccording to claim 14, wherein at least one of the second inductor orthe second capacitor is variable.